The number of employed older workers fell last month, possibly a sign that President Obama’s law reforming health care is enabling them to leave their jobs, a prominent left-leaning economist said Friday.

Last month the number of employed workers who were at least 55-years old fell by 133,000, the largest drop in half a year, according to U.S. Labor Department data. Trends also show a slowdown: Over the first quarter of the year, there was an average monthly gain of 86,000 employed older workers, down sharply from a peak of almost 300,000 two years earlier.

“It is possible that the [Affordable Care Act] is allowing many of these workers to retire early now that they can get health care insurance outside of employment,” said Dean Baker, co-director of the Center for Economic and Policy Research.

It will be a few years before the ACA’s full labor-market impact is seen, he added.

“I think a drop in employment of 2% among older workers is certainly plausible,” Baker said. “We’ll see something among younger workers as well, primarily parents of small children.”

However, Baker warned that the data are volatile, and it’s still early days in the ACA’s implementation, so observers should be careful about drawing firm conclusions from March’s data.

Also of note, the unemployment rate for older workers ticked up last month to 4.7% from 4.6% in February, indicating that some workers were involuntarily out of a job.